The Second International Lymphokine Workship decided to adopt a unified name, interleukin-1 (IL-1), for the physiologically active substances which had been referred to as lymphocyte activating factor (LAF), mitogenic protein, helper peak-1, T-cell replacing factor III (TRF-III), T-cell replacing factor M.phi. (TRFM), B-cell activating factor, B-cell differentation factor, etc. (Cellular Immunol., 48, 433-436 (1979)). This decision is based on the reason that these physiologically active substances can not be distinguished from one another as different substances but are expressed variously merely with reference to physiological activities as interpreted from different angles.
Further it is reported that IL-1 activates T lymphocytes and B lymphocytes, has activity to promote production of interleukin-2 and antibodies, acts on liver tissues to promote protein synthesis and possesses activity to promote production of prostaglandins (see Reviews of Infectious Disease, Vol. 6, No.1, 51-59 (1984), New England J. of Med., 311, 1413 (1984), etc.).
Whereas IL-1 itself still remains to be clarified as a substance, it is only recently that reports are made on the presence of two different genes coding for polypeptides having LAF activity or precursor thereof (Proc. Natl. Acad. Sci., Vol. 81, 7907-7911 (1984), Nature, Vol. 315, 641 (1985), Nucleic Acid Research, Vol. 13 (16), 5869 (1985)). These reports mention "IL-1.alpha." having a sequence of 159 amino acids and "IL-1.beta." comprising 153 amino acids which are postulated from the base sequences of the two genes.
Nevertheless, research has yet to be made to clarify the relation between said activities assayed using a conditioned medium or so called partially purified IL-1 and the polypeptide postulated from the above base sequences.
Known IL-1 as a physiologically active substance is also thought to be identical with an endogeneous pyrogen (EP) and is known to exhibit a pyrogenic property (see Nature, 304, 449 (1983); Cell Immunol., 63, 164 (1981); J. Exp. Med., 150, 709 (1979); J. Immunol., 130, (6) 2708 (1983); same, 132 (3) 1311 (1984); etc.). This indicates that IL-1, if available as a uniform substance, to say nothing of physiologically active conventional IL-1, is difficult to use for medical applications.